Wednesday, 3 February 2016

Eww! Are those maggots in my compost bin?

I have been trying very hard to get my compost bin to work. I've been worried about the carbon to nitrogen ration, about what I put in there, and whether it was wet enough.

I started with some dry leaves and sticks in the bin, then I dumped a whole heap of shredded paper and cardboard into the bin and then started to layer scraps and paper. Once we got the chickens, I started to put their litter in there as well, and also the rat litter.

One problem was fruit. Whenever I put fruit leftovers into the bin the fruit fly clouds that would come out of the bin was a worry! I didn't want to get any fruit flies into my mouth or my nose! I thought that if I kept covering the fruit with more carbon (paper and cardboard) I could get rid of the flies.

Every time I put something in the compost bin I would anxiously check it to see if the contents were "going down". It didn't seem to be decreasing in size - was the pile of compost going to get bigger and bigger and I would be left with a stinking, rotting pile of unusable sludge rubbish? I so desperately wanted to have good quality compost so I could reuse it for gardening! I had read in many places that "good compost" should smell like dirt or straw, and not stinky like rotten eggs. The worm farm smelled like dirt, so I knew that the worm farm must be going ok.

Yesterday, I had a bit of a shock.

I went out to put things into the compost bin and when I looked inside, the top of the pile was moving. I saw a grub crawling up the side of the bin, and it looked very juicy. I wondered what it was. I looked back at the rest of the compost and saw there were TONS of these things writhing around in the food.

OMG, there were MAGGOTS in my compost bin!

This is not what I saw. What I saw were bigger and fatter than these, and not so numerous. But you get the idea.

I quickly dropped the scraps in the bin and ran into the house to check Google. I hadn't put any rotting meat there, so why are there maggots in the bin? I thought about it, and maggots eat rotting things so they SHOULD be a good thing right?

It turns out that these weren't just ordinary house fly maggots. They were in fact Black Soldier fly larvae.

BSF laying eggs in corrugated cardboard. They like to lay NEAR rotting stuff but not on top of it.

These guys are actually FANTASTIC things to have in the compost. You know, ever since I was young I had seen these flies but thought they were some kind of wasp like insect but with no sting. I'd seen them sitting on plants at my parent's house in the garden, and they didn't buzz or swarm around you, they would just quietly sit there. I had actually seen one in my own garden the other day, and I had just dismissed it as another garden insect. And I hadn't actually noticed at the time, but there was no swarm of fruit flies coming out of the compost like it had on other days.

The Black Soldier Fly larvae are beneficial in a number of ways:
They prevent houseflies and blowflies from laying eggs in the material inhabited by black soldier fly larvae, and unlike common house flies, they are not attracted to human habitation or foods. They don't fly around as much as houseflies and are easy to catch and relocate when they get inside a house, as they don't avoid being picked up. Because they have no mouth, they are sanitary, and they do not bite or sting. Their only defense seems to be hiding.

They quickly reduce the volume and weight of compostable organics because they are voracious eaters - it's because they eat so fast that other insects don't have a chance to get in and establish. They even eat meat and dairy - things that I hadn't been putting into the compost bin. According to the ESR International, 45 kilos of food waste will produce 2.3kg of usable compost and 9 kilos of larvae. They do well in warmer temperatures - apparently 30 degrees is what they need to grow and reproduce - and the emerging adult fly only lives a few days, and its sole purpose is to breed and then die. However, they keep themselves warm in winter as all that eating produces heat, so if your mass of larvae is big enough they can keep themselves warm. And in the summer, when there are too many of them and it gets too hot, some will crawl away and the mass reduces to a manageable size.

These larvae are apparently an amazing source of nutrition.
An Analysis of Dried Soldier Fly Prepupae by ESR International showed that the nutritional information of dried larvae contained:

Are these chickens thinking "Yum?" or "Eww what is that?" I'm going for the former.

There is apparently a large industry and demand for these larvae! There are companies in the world who recycle all organic waste (including faeces) with these grubs, and in turn take these larvae and turn it into livestock feed. There are companies who make containers just for harvesting BSF larvae and you can even get them in Australia.

So, now I was all excited about my latest inhabitants of the compost bin. I took the kids out to look at the moving mass, and got excited about feeding them. I hoped that they would keep reinfesting my compost bin so that the biomass would go down and I'd get a nice lot of usable compost. I wished that I had some way to harvest the larvae for the chickens when they were bigger, but how would I get in there? It was scared I'd fall into the Aerobin trying to get them out. I guess I should just leave them there to reproduce and make more larvae for me, rather than feed them to the chickens all the time. But it would be rather cool if I could get them separated.

So that's the great thing about having a worm farm and a BSF larvae farm. The BSF larvae don't like cellulose from plant stems or cardboard and paper, but they love rotting vegies, fruits, and a bit of meat and dairy - and even onion and citrus. The worms however love to eat paper and cardboard as well as vegies and a bit of fruit (but not citrus or onion). You can't actually put the two together, because the BSF larvae will eat the worms out of house and home, and also the BSF larvae like it hot, but the worms like it cool.

I thought it was cool to see nature in action, but it was interesting when doing internet searches on the subject how many people thought it was abhorrent or unhealthy to have these larvae in your compost bin (and slaters too!) and ways to prevent them from proliferating in your bin. I can't think of anything more morbidly exciting!

It's now a thrill every day to open up the compost bin and have a look inside to see if the larvae/maggots are squirming around gobbling up yesterday's leavings. I can't tell you how great it is to know that my compost bin is doing the right thing! I've been collecting all my sister's kitchen scraps as well (since she lives close by) and I feel like I'm doing something good for the environment. I wish everyone would have a compost bin!